linux-stable.git/drivers/tty/vt/selection.c, branch linux-4.8.y

tty: Replace TTY_THROTTLED bit tests with tty_throttled()

2016-04-30T16:26:55+00:00

Abstract TTY_THROTTLED bit tests with tty_throttled().

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

tty: Prepare for destroying line discipline on hangup

2016-01-27T23:01:44+00:00

tty file_operations (read/write/ioctl) wait for the ldisc reference
indefinitely (until ldisc lifetime events, such as hangup or TIOCSETD,
finish). Since hangup now destroys the ldisc and does not instance
another copy, file_operations must now be prepared to receive a NULL
ldisc reference from tty_ldisc_ref_wait():

CPU 0                                   CPU 1
-----                                   -----
(*f_op->read)() => tty_read()
                                        __tty_hangup()
                                        ...
                                        f_op = &hung_up_tty_fops;
                                        ...
                                        tty_ldisc_hangup()
                                           tty_ldisc_lock()
                                           tty_ldisc_kill()
                                              tty->ldisc = NULL
                                           tty_ldisc_unlock()
ld = tty_ldisc_ref_wait()
/* ld == NULL */

Instead, the action taken now is to return the same value as if the
tty had been hungup a moment earlier:

CPU 0                                   CPU 1
-----                                   -----
                                        __tty_hangup()
                                        ...
                                        f_op = &hung_up_tty_fops;
(*f_op->read)() => hung_up_tty_read()
return 0;
                                        ...
                                        tty_ldisc_hangup()
                                           tty_ldisc_lock()
                                           tty_ldisc_kill()
                                              tty->ldisc = NULL
                                           tty_ldisc_unlock()

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

tty: vt: Fix !TASK_RUNNING diagnostic warning from paste_selection()

2015-07-24T01:08:29+00:00

Pasting text with gpm on a VC produced warning [1]. Reset task state
to TASK_RUNNING in the paste_selection() loop, if the loop did not
sleep.

[1]
WARNING: CPU: 6 PID: 1960 at /home/peter/src/kernels/mainline/kernel/sched/core.c:7286 __might_sleep+0x7f/0x90()
do not call blocking ops when !TASK_RUNNING; state=1 set at [] paste_selection+0x9e/0x1a0
Modules linked in: btrfs xor raid6_pq ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs libcrc32c .....
CPU: 6 PID: 1960 Comm: gpm Not tainted 4.1.0-rc7+tty-xeon+debug #rc7+tty
Hardware name: Dell Inc. Precision WorkStation T5400  /0RW203, BIOS A11 04/30/2012
 ffffffff81c9c0a0 ffff8802b0fd3ac8 ffffffff8185778a 0000000000000001
 ffff8802b0fd3b18 ffff8802b0fd3b08 ffffffff8108039a ffffffff82ae8510
 ffffffff81c9ce00 0000000000000015 0000000000000000 0000000000000000
Call Trace:
 [] dump_stack+0x4f/0x7b
 [] warn_slowpath_common+0x8a/0xc0
 [] warn_slowpath_fmt+0x46/0x50
 [] ? __lock_acquire+0xe2d/0x13a0
 [] ? paste_selection+0x9e/0x1a0
 [] ? paste_selection+0x9e/0x1a0
 [] __might_sleep+0x7f/0x90
 [] down_read+0x2a/0xa0
 [] ? sched_clock_cpu+0xb8/0xe0
 [] n_tty_receive_buf_common+0x4c/0xba0
 [] ? mark_held_locks+0x75/0xa0
 [] ? _raw_spin_unlock_irqrestore+0x65/0x80
 [] ? get_parent_ip+0x11/0x50
 [] n_tty_receive_buf2+0x14/0x20
 [] paste_selection+0x157/0x1a0
 [] ? wake_up_state+0x20/0x20
 [] tioclinux+0xb8/0x2c0
 [] vt_ioctl+0xaee/0x11a0
 [] ? sched_clock_local+0x25/0x90
 [] ? vtime_account_user+0x91/0xa0
 [] tty_ioctl+0x20c/0xe20
 [] ? vtime_account_user+0x91/0xa0
 [] ? get_parent_ip+0x11/0x50
 [] ? preempt_count_sub+0x49/0x50
 [] ? context_tracking_exit+0x5c/0x290
 [] ? context_tracking_exit+0x5c/0x290
 [] do_vfs_ioctl+0x318/0x570
 [] ? trace_hardirqs_on+0xd/0x10
 [] ? trace_hardirqs_on_caller+0x115/0x1e0
 [] ? __fget_light+0x6c/0xa0
 [] SyS_ioctl+0x81/0xa0
 [] system_call_fastpath+0x16/0x7a

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

tty: Fix unsafe vt paste_selection()

2013-07-23T23:47:10+00:00

Convert the tty_buffer_flush() exclusion mechanism to a
public interface - tty_buffer_lock/unlock_exclusive() - and use
the interface to safely write the paste selection to the line
discipline.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

tty: Make ldisc input flow control concurrency-friendly

2013-07-23T23:42:59+00:00

Although line discipline receiving is single-producer/single-consumer,
using tty->receive_room to manage flow control creates unnecessary
critical regions requiring additional lock use.

Instead, introduce the optional .receive_buf2() ldisc method which
returns the # of bytes actually received. Serialization is guaranteed
by the caller.

In turn, the line discipline should schedule the buffer work item
whenever space becomes available; ie., when there is room to receive
data and receive_room() previously returned 0 (the buffer work
item stops processing if receive_buf2() returns 0). Note the
'no room' state need not be atomic despite concurrent use by two
threads because only the buffer work thread can set the state and
only the read() thread can clear the state.

Add n_tty_receive_buf2() as the receive_buf2() method for N_TTY.
Provide a public helper function, tty_ldisc_receive_buf(), to use
when directly accessing the receive_buf() methods.

Line disciplines not using input flow control can continue to set
tty->receive_room to a fixed value and only provide the receive_buf()
method.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

TTY: vt, fix paste_selection ldisc handling

2012-10-22T23:50:53+00:00

There used to be a single tty_ldisc_ref_wait. But then, when a
big-tty-mutex (BTM) was introduced, it has to be tty_ldisc_ref +
tty_unlock + tty_ldisc_ref_wait + tty_lock. Later, BTM was removed
from that path and tty_ldisc_ref + tty_ldisc_ref_wait remained there.
But it makes no sense now. So leave there only tty_ldisc_ref_wait.

And when we have a reference to an ldisc, actually use it in the loop.
Otherwise it may be racy.

Signed-off-by: Jiri Slaby 
Acked-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

vt: tackle the main part of the selection logic

2012-03-08T19:11:39+00:00

We leave the existing paste mess alone and just fix up the vt side of
things.

Signed-off-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

vt: push down tioclinux cases

2012-03-08T19:10:27+00:00

Some of this ventures into selection which is still a complete lost cause. We
are not making it any worse. It's completely busted anyway.

Signed-off-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

vt:tackle kbd_table

2012-03-08T18:50:35+00:00

Keyboard struct lifetime is easy, but the locking is not and is completely
ignored by the existing code. Tackle this one head on

- Make the kbd_table private so we can run down all direct users
- Hoick the relevant ioctl handlers into the keyboard layer
- Lock them with the keyboard lock so they don't change mid keypress
- Add helpers for things like console stop/start so we isolate the poking
  around properly
- Tweak the braille console so it still builds

There are a couple of FIXME locking cases left for ioctls that are so hideous
they should be addressed in a later patch. After this patch the kbd_table is
private and all the keyboard jiggery pokery is in one place.

This update fixes speakup and also a memory leak in the original.

Signed-off-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

TTY: remove tty_locked

2011-08-23T17:34:07+00:00

We used it really only serial and ami_serial. The rest of the
callsites were BUG/WARN_ONs to check if BTM is held. Now that we
pruned tty_locked from both of the real users, we can get rid of
tty_lock along with __big_tty_mutex_owner.

Signed-off-by: Jiri Slaby 
Acked-by: Arnd Bergmann 
Cc: Alan Cox 
Signed-off-by: Greg Kroah-Hartman